Disk drives are information storage devices that utilize at least one rotatable disk with concentric data tracks containing the information, a transducer (or head) for reading data from or writing data to the various tracks, and a transducer positioning actuator connected to the transducer for moving it to the desired track and maintaining it over the track during read and write operations. The transducer is attached to a slider, such as an air-bearing slider, which is supported adjacent to the data surface of the disk by a cushion of air generated by the rotated disk. The transducer can also be attached to a contact-recording type slider. In either case, the slider is connected to a support arm of the transducer-positioning actuator by means of a suspension.
The suspension provides dimensional stability between the slider and the actuator arm, controlled flexibility in pitch and roll motion of the slider relative to its direction of motion on the rotating disk, and resistance to yaw motion. In conventional disk drives having air-bearing sliders, the suspension provides a load or force against the slider which is compensated by the force of the air-bearing between the slider's air-bearing surface and the disk surface. Thus, an air-bearing slider is maintained in extremely close proximity to, but out of contact with, the data surface of the disk. The suspension typically comprises a load beam, which is mounted at one end to the actuator arm, and a flexure element which is attached to the other end of the load beam and whose gimbal area supports the slider. The load beam provides the resilient spring action which biases the slider toward the surface of the disk. This spring action provides flexibility for the slider as the slider rides on the cushion of air between the airbearing surface and the rotating disk. Also, the gimbal provides roll and pitch flexibility needed for the slider to follow the dish surface. Such a suspension is described, for instance, in assignee's U.S. Pat. No. 4,167,765. An example of a conventional slider for use with such a suspension is described in assignee's U.S. Pat. No. 3,823,416.
In a conventional air-bearing slider-suspension assembly, the slider is mechanically attached to the flexure element of the suspension by epoxy bonding. The electrical connection between the transducer and the read/write electronics is made of twisted wires which run the length of the suspension load beam and extend over the flexure element and the slider. The ends of the wires are soldered or ultrasonically bonded to the transducer bonding areas or pads located on the slider. Another type of suspension is a composite or laminated structure comprising a base layer with patterned electrical leads formed thereon and an insulating cover layer, as described in IBM Technical Disclosure Bulletin, Vol. 22, No. 4 (Sep. 1979), pp. 1602-1603 and Japanese Kokai Nos. 53-74414 (Jul. 1, 1978) and 53-30310 (Mar. 22, 1978). In the laminated suspension described in Japanese Kokai No. 53-74414, the slider is epoxy-bonded to the laminated suspension and the transducer bonding areas are soldered to the electrical leads formed on the suspension. Assignee's U.S. Pat. No. 4,761,699 describes a laminated suspension for use with a conventional slider wherein solder ball connections provide both the mechanical connection of the slider to the laminated suspension and the electrical connection of the transducer to the leads on the laminated suspension.
Assignee's U.S. Pat. No. 4,996,623 describes yet another type of laminated suspension for use with a negative pressure slider. For this type of suspension, it is desirable to maintain the slider adjacent to the data surface of the disk with as low a loading force as possible. The suspension is a flat, flexible sheet of material bonded on both sides to patterned metal layers and having hinge regions. Portions of the laminated suspension near the hinge regions are bent such that the suspension supports the slider in a manner to prevent the transducer from contacting the disk surface. Thus, the stiction problem associated with the negative pressure slider and the disk surface is eliminated.
One of the problems with disk drives using the conventional suspension or the laminated type suspension is that the ill-defined characteristic impedance of the electrical conductors prevents reliable, high data-rate transfer between the transducer and the read/write electronics. For instance, in disk drives with a data rate greater than approximately 15 million bytes per second, a large bandwidth is required between the transducer and the read/write electronics for transmitting data at very high frequencies. This requirement is particularly critical in the transmission of nearly rectangular write signals or where the connection distance is large, for instance 5 to 6 cm in a 3.5" disk drive. The characteristic impedance of a twisted conductor depends partially on the wire diameter, the insulation thickness, the number of twists per unit of length, the tightness of the twists, and its proximity to the ground plane. Furthermore, the characteristic impedance of a conductor normally does not remain uniform over the length of the conductor due to changes in its shape, in its spacing from other conductors, or in the area adjacent to the trace. These changes are usually required to accommodate mechanical obstructions in the trace's path. For example, a conductor may be narrowed in some areas or changed in its direction to accommodate openings and corrugations in the suspension, or holes in the suspension used for mechanical alignment. The characteristic impedance of a conductor may also be changed where it is located directly above an aperture required for a hinge in the suspension. Finally, it may be necessary to alter the shape of a conductor to achieve a desired characteristic impedance of the conductor for accommodating a particular type of transducer or read/write electronic design.
The present invention solves the above problem by providing the conductors as electrically conductive traces in the laminated structure of the suspension. The shapes of the traces are varied to avoid abrupt changes in the characteristic impedance of the traces or to obtain a specific impedance value where needed. Another technique for controlling the trace impedance is to provide an electrically conductive back plane in the laminated structure of the integrated head-electronics interconnection suspension. The characteristic impedance of selected portions of the traces can then be adjusted by removing portions of the back plane under the traces.
Another problem with disk drives using the conventional suspension or the laminated type suspension is that the twisted conductors can easily break off during the manufacture of the suspension-slider assembly. This problem arises since the soldering and twisting of the conductors are normally done by a machine in the automated manufacturing of the suspension. The integrated suspension of the present invention eliminates the breakage of the conductors by including them as a part of the suspension's laminated structure. It thus facilitates the manufacture of the suspension and lowers its manufacturing cost by improving the yield.